Spark-plug.



F. M. URBER.

SPARK PLUG.

APPLICATION FILED AUG.22,1912.

Patented Jan. 13, 1914 AVENUR. @MMM @l QM STATES- PATENT oFFioE.

I 'REDERICK il. FURBER, 0F BEAQHIQNJ, MASAQHUSETN I SPARK-PLUG.

Specicatieu of Letters Patent,

Application filed August 22, 1912.' Serial No. 716,420.

To all whom t may concern.'

Be it known that I, FREDERICK M. FURBER, a citizen of the United States, residing at 1^ Beachmont, in the county of Suiolk and State of Massachusetts, have invented certain"v Improvements in Spark-Plugs, ofY

Considerable trouble is experienced With the wrench. The interior 4of the body is reamed devices of this character commonly used in internal combustion engines due to the cracking of the insulator that electrically separates the electrodes. Thisresult is caused partly by the fact that too great pressure often is applied to the insulator by the clamping devices that hold it in the plug, but more particularly by the fact that the insulator is unable to withstand the pressure produced by the sudden and extreme changes in tenperature'to which it is subjected While in use.

It is a particular object of this invention to devise a construction in which liability of injury to the insulator from these causes shall be eliminated.

The invention further aims to provide a deviceot this character which, While of substantial and durable construction, can be cheaply manufactured.

The invention will be readily understood from the following description When read in connection with the accompanying drawings, in Which- Figure 1 is a perspective view of a spark plug constructed in accordance with the invention.; and Fig. 2 is a central, iong-jf'idiil il sectional view of the device shown in Fig.

The spark plug shown comprises a body 2 which may be made from tubular stock having a hexagonal cross sectional outline. This body is turned down for a considerable distance back from one end and the turned portion is threaded to enable the body to be screwed into an engine cylinder' in the usual manner, the unturned portion having'suitable surfaces for the application thereto of a 'out to form a borethat is cylindrical for a distance frommthe inner` end of .the body (that is, the end that is tobe inserted in the c lvlinder) y the outer end of the body. It will be eviand then tapers gradually toward\\ l dent that all the machine Work on the body can be performed automatically in a screw machine.

A bushing 4, tapered to conform to the tapered portion of the bore in the body 2, is fitted snugly into said bore and is provided with an out-turned flanve 6 resting upon 1the outer e'nd of the bo y. The in-v sulator 8, which may be madeof orcelain, lava, or'any other suitable materlal, has a tapered portion itting snugly Within the bushing 4t. Below this tapered portion the shoulder 10 which forms a seat for an inturned flange 12 provided at the inner end 'of the bushing 4.

It will be clear from an inspection of Fig. 2 that the arrangement of tapers above described locks the insulator against movement out` of the body 2 in one direction,- While the bushing' t With its flanges 6 and 12 prevents any movement of the insulator in the opposite direction. Preferably, the bushing 4 is made of soft metal such, for instance, as aluminum, (although many other metals. and alloys maybe used 'for this purpose) since a material of this' character seems to yield suiiiciently to maintain a tight joint between the body and the insulator, and yet relieves to some extent the pressure to which the insulator is subjected due to ing the cracking of the insulator above described. The bushing 4 may consist merely otra piece of tubing of substantially uniform thickness, thetapered form being produced by forcing a suitably shaped plunger into it.

The plug may be assembled by inserting the insulator 8 in the bushing 4, the bushing p 'eviously having been tapered as above described, and then swaging the inner end of the bushing over the shoulder 10 to form the fiangelQ. The insulator and bushing may then be forced into the body 2 and held iirnily in the tapered portion of the bore while the outer end of the bushing is swaged over to form the flange G. A preferable method of asscnxbling the plug, however, consists in forcing the piece of tubing, which later will torni the bushing 4, into the body 2 by means of a suitably tapered plunger while the body is heated to a temperature high as the maximum temperature to which it will be subjected in use. The outer end of the body should be supported during this operation on a die shaped insulator is reduced in diameter, forming a.

Patented Jam` 13, 1914. i

sudden changes in temperature, thus avoidto turnover the end of the `bushing t so that this operation will shane the bushing to the taper of the body and also form the flange 6. After this o eration the insulator is forced into the bus ing et andthe inner end ot' the bushin vis swaged over the shoulder 10 by a suitab y shaped tool. This construction avoids the use of clamping devices for holding ythe insulator that can be operated by the user of the plug to increase the pressure on the insulator with the consequent liability of breaking it.

lThe electrodes may be of any convenient construction. As shown, one electrode 14 consists of a pin extending diametrieally across the bore of the body 2 and having its ends supported in said body close to the inner extremity of the body. A coperating electrode, comprising an electrode tip 16 made of any Well known material capable of resisting the disintegrating action of the spark, is set intothe end of an electrode rod 18 that is provided with a shoulder 20, Which is seated at the end of a counter bore formed in the insulator 8 and coperates with a Washer resting on the outer end ofthe insulator, and a nut 22 threaded on the rod 18 and bearino' against said Washer to secure the rod firmly in the insulator. A binding nut 2&1 also is threaded on to the electrode rod 18 and serves to clamp in operative position the conductor by which the plug is connected to the ignition system. It desired, one end of the V body 2 may be utilized as one electrode and the electrode 111 may be omitted, the electrode rod 18 being bent to position the tip 1G Within sparking distance of the Wall of the body.

Having thus described my invention, what g p :ees/.11,543

an insulator positioned in said bo y and having a portion tapered l1n the direction of the taper of said bore, a bushing interposed be tween and in engagement with the tapered surfaces of said insulator and saidbody and serving to hold the insulator against movement out of the body in one direction7 said bushing having parts engagino respectively with said body and said insulator and operating to hold the insulator against movement out of the body in the opposite direcn tion, and electrodes electrically separated by saidl insulator.

2. A device of the character described comprising 4a body having an externally threaded portion and a4 bore formed therethrough tapered toward the outer end of said body, a tapered bushing of substantially uniform thickness fitting in the tapered portion of said bore, an insulator tapered to conform substantially to the taper of said bushing and fitting in said bushing, said insulator havin a reduced shoulder Within said body, an inturned flange ou said bushing engaging said shoulder, an outturned flange on said bushing engaging the outer end of said body, and electrodes electrically separated by said insulator.

ln testimony whereof I'have signed my name to this specification in the presence of two subscribing Witnesses.

FREDERICK M. FURBER.

Witnesses Sornnoizm l. Manen, HAnLow M. Dnvis. 

